net: add CONFIG_PCPU_DEV_REFCNT

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I was working on a syzbot issue, claiming one device could not be
dismantled because its refcount was -1

unregister_netdevice: waiting for sit0 to become free. Usage count = -1

It would be nice if syzbot could trigger a warning at the time
this reference count became negative.

This patch adds CONFIG_PCPU_DEV_REFCNT options which defaults
to per cpu variables (as before this patch) on SMP builds.

v2: free_dev label in alloc_netdev_mqs() is moved to avoid
    a compiler warning (-Wunused-label), as reported
    by kernel test robot <lkp@intel.com>

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Eric Dumazet 2021-03-19 10:39:33 -07:00 • committed by David S. Miller

parent 942f0c6e28

commit 919067cc84

3 changed files with 31 additions and 0 deletions

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include/linux/netdevice.h

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